Process of preparing transfer media



Dec. 14, 1965 D. A. NEWMAN PROCESS OF PREPARING TRANSFER MEDIA Filed Oct. 22, 1962 L 1 O y I fly Z 25 con Due T/VE METALLIC COAT/N6 Z K ,fiZd-FZEXABLE FOUND/4770M INVENTOR. DoqgZczs .4. Newman United States Patent 3,223,554 PROCESS OF PREPARING TRANSFER MEDIA Douglas A. Newman, Glen Cove, N.Y., assignor to Columbia Ribbon and Carbon Manufacturing C0., Inc., Glen Cove, N.Y., a corporation of New York Filed Oct. 22, 1962, Ser. No. 232,111 7 Claims. (Cl. 117-217) This application is a continuation-inpart of Serial No. 814,961, filed May 22, 1959, now abandoned.

This invention relates to pressure-sensitive transfer elements such as carbon papers and typewriter ribbons, and more particularly to such elements on which the transfer layer is applied by means of volatile organic solvents to a flexible foundation, and to the novel method of preparing the same.

Although carbon papers have been conventionally prepared for many years by applying the transfer layer as a hot-melt wax composition, the modern trend in the duplicating field is directed towards the use of transfer layers based upon plastic binder materials and applied as volatile organic solvent solutions.

Transfer layers applied by means of volatile solvents offer many advantages over conventional hot-melt wax compositions. Solvent coatings based upon either Wax or resin binder materials may be applied as thinner and more uniform layers than hot-melt compositions. Solvent coatings are applied at room temperature and do not present the impregnation and staining problems encountered with the molten wax and hot oils when applying hot-melt compositions to paper foundations. Also, solvent coatings based upon plastic binder materials are cleaner to the touch, produce more smudge-resistant duplicate images and are resistant to becoming too soft or too hard when the temperature is varied.

Although there are numerous advantages to the use of transfer layers applied by means of volatile organic solvents, there are also numerous disadvantages which are encountered during the manufacture of transfer elements containing thesame. Since the transfer composition is applied by means of solvents, the coating equipment must include a drying tunnel or passage which may be 30 or more feet in length, wherein the volatile solvent is evaporated after the coating is applied. Thus the length of flexible foundation exposed to the atmosphere from the time the film is expended from one roll, coated, dried and taken up on a second roll is far greater than is the case with hot-melt compositions. Although filtering precautions are taken, it is found that much dust and dirt is accumulated on the foundation, attracted by static attraction, and has a very deleterious effect upon the imaging properties of the sheet or ribbon prepared.

Paper webs and plastic films have the tendency to accumulate and build up static electricity on their surface during processing so that when a long stretch of the paper or film is exposed a potentialof several thousand volts may be encountered if the web is inadvertently touched. The static problem is much greater with plastic films than with paper since plastic films tend to build up a much higher potential. In either case I have found that the static charge on the foundation has the tendency to attract dust and dirt from the atmosphere. However, in the case of plastic films, the tendency of the high potential thereon to be discharged in the area of the drying tunnel of the solvent coating apparatus and to cause an explosion of the highly volatile organic solvent vapors is much greater than in the case of paper foundations.

Another problem commonly encountered with transfer elements having a plastic film foundation is their tendency to be attracted together by static attraction which makes them difficult to handle, separate, align with copy 3,223,554 Patented Dec. 14, 1965 sheets for insertion into a typewriter or unwind, in the case of ribbons. This problem is particularly critical in the case of films of small caliper or thickness in the area of 1 mil or less.

It is an object of the present invention to overcome some of the problems encountered during the manufacture of organic solvent-coated transfer sheets and ribbons and to produce such sheets and ribbons in a cleaner and safer manner than heretofore possible.

It is another object of this invention to prepare organic solvent-coated transfer sheets and ribbons on which the transfer layer is relatively free of dust and dirt and which therefore perform more uniformly and reliably than those heretofore known.

It is an advantage of this invention that plastic transfer sheets and ribbons are produced which are easier to handle than those heretofore known.

These and other objects and advantages of this invention are accomplished as will be obvious to those skilled in the art in the light of the following disclosure.

In the drawings:

FIGURE 1 is a schematic view of the coating system used according to this invention.

FIG. 2 is a diagrammatic cross-section, to an enlarged scale, of a transfer element produced according to this invention.

The objects and advantages of the present invention are attained by the use of a conductive metallic coating on the flexible foundation of the present transfer sheets.

It has been found that such a foundation may be handled, rolled, coated and otherwise treated in a much simpler fashion than an untreated foundation provided that the conductive metallic coating is grounded to allow the static charges to be conducted away from the foundation.

In this manner the problem of static build-up or acmumulation is avoided and the tendency of the foundation to attract dust and dirt from the atmosphere is overcome. Likewise the possibility of explosion and fire due to ignition of solvent vapor by static discharge is also avoided.

This invention is applicable to all types of flexible foundations having the tendency to accumulate static electricity, including paper and conventional plastic film foundations. The most important plastic films for use according to this invention presently appear to include polyethylene terephthalate (Mylar), polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride (Saran), polyethylene, polypropylene, cellulose acetate and cellophane.

The film foundation is coated with a conductive metal such as silver, copper, nickel, chrome or the like. The preferred method is to apply a thin vacuum coating of silver in conventional manner, the silver coating having a minute thickness so as to be as inexpensive as possible and not to affect the original flexibility of the film foundation. There appears to be no lower limit on the amount of metallic coating which can be applied so long as the coating is relatively continuous, thereby allowing the static charges to be conducted from the foundation. The preferred metallic coatings are so thin that they are actually transparent when held close to the eye.

In practice, a plastic film such as 0.5 mil Mylar is vacuum coated with from about 1.5 pounds to about 10 pounds of a metallic silver composition per pounds of the film.

Next the metal-coated foundation, which is grounded on the roll and/or at various locations along the stretch of web to be coated, is coated with the solvent-applied transfer composition which is applied preferably to the surface of the plastic film but which may be applied over the metallic layer if desired.

As shown in FIG. 1 of the drawing, the metal-coated foundation 2 is expended from grounded roll 1, passes over grounded idler rollers 3 and 4 and makes contact with application roller 5 which is immersed below the surface of the ink solution 7 in vat 6. The web carrying the wet ink composition as layer 8 passes over grounded idler roller 9 and through heating tunnel 10 where the solvent is evaporated to dry the ink coating and form dry transfer coating 11. Finally the web is taken up on roll 12 and sheets or ribbons are cut therefrom having flexible foundation 2a, conductive metallic coating 2b and transfer layer 11 as illustrated by FIG. 2.

In the course of the coating operation the foundation is prevented from accumulating a static charge by means of the metallic layer in combination with the grounded roll and rollers whereby the static electricity is conducted from the foundation through the metallic coating to the ground. Thus the foundation is prevented from attracting dust and dirt from the atmosphere and the possibility of explosion or fire due to static discharge in the area of the drying tunnel is avoided.

The following procedure is set forth merely by way of illustration and should not be considered as limiting the scope of this invention.

A wide web of Mylar polyethylene terephthalate polyester film having a thickness of 0.5 mil was vacuum coated on one side with a continuous coating of silver in an amount of 3 pounds per 100 pounds of film.

The silver coated film was rolled on a grounded roll and then coated on the surface of the film opposite the metal coating with a volatile organic solvent solution of a transfer composition comprising vinyl chloride-vinyl acetate copolymer binder material, mineral oil, carbon black, ethyl acetate and toluol in the manner illustrated by FIG. 1 of the drawing.

The final web taken up on roll 12 was free of static electricity, had no tendency to cling and was easy to unroll, cut and handle.

As is obvious to those skilled in the art in view of the foregoing teachings, this invention applies to volatile organic solvent-applied transfer layers of all types including the pressure-sensitive squeeze-out type carbon layers as defined for instance by my US. Patent No. 3,037,879 in which the binder material is resinous and porous and non-transferable while the oil and pigment are squeezed out under imaging pressure to form a copy; and also including the more conventional stenciling-type transfer layers of the carbon paper, hectograph and magnetic pigment types in which the binder material may be wax, resin or a mixture thereof. Illustrative of these types are my U.S. Patent Nos. 3,036,924, 2,872,340 and 2,606,775.

As further disclosed in my aforementioned US. Patent No. 3,037,879, the transfer elements of this invention may also contain an intermediate layer between the flexible foundation and the transfer layer, the object of said intermediate layer being to bind or adhere the transfer layer to the foundation and prevent the same from peeling or cracking from the foundation prior to use. This consideration is more important in the case of plastic film foundations and is preferably met by the use of intermediate layers which are based upon or consist solely of plastic materials such as the vinyl resins.

Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.

I claim:

1. The process of avoiding the hazards of static electricity while coating a continuous flexible foundation having a tendency to accumulate static electricity with an organic solvent-applied transfer composition, which comprises coating said foundation with a thin flexible conductive metal layer, grounding said metal-coated foundation to allow the static electricity to be conducted therefrom and coating said grounded metal-coated foundation with a layer of transfer composition comprising binder material, imaging material and a volatile organic solvent, and evaporating said solvent to solidify said transfer composition and form a pressure-sensitive transfer layer on said metal-coated foundation while the foundation is maintained grounded, thereby avoiding the possibility of static accumulation which attracts deleterious dust into the transfer composition and avoiding the possibilty of static discharge which could cause combustion of the organic solvent particularly during the evaporation thereof.

2. The process according to claim 1 in which the flexible foundation is a plastic film.

3. The process according to claim 1 in which the binder material is a resinous binder material.

4. The process of avoiding the hazards of static electricity while coating a continuous flexible film foundation having a tendency to accumulate static electricity with an organic solvent-applied transfer composition, which comprises vacuum coating said foundation with a thin flexible conductive metal layer, grounding said metal-coated foundation to allow the static electricity to be conducted therefrom and coating said grounded metal-coated foundation with a layer of transfer composition comprising binder material, imaging material and a volatile organic solvent, and evaporating said solvent to solidify said transfer composition and form a pressure-sensitive transfer layer on said metal-coated foundation while the foundation is maintained grounded, thereby avoiding the possibility of static accumulation which attracts deleterious dust into the transfer composition and avoiding the possibility of static discharge which could cause combustion of the organic solvent particularly during the evaporation thereof.

5. The process according to claim 4 in which the flexible foundation is a plastic film.

6. The process of avoiding the hazards of static electricity while coating a continuous flexible plastic film foundation having a tendency to accumulate static electricity with an organic solvent-applied transfer composition, which comprises vacuum coating said foundation with a thin flexible conductive metal layer, grounding said metal-coated foundation to allow the static electricity to be conducted therefrom and coating said grounded metal-coated foundation with a layer of transfer composition comprising resinous binder material, imaging material and a volatile organic solvent, and evaporating said solvent to solidify said transfer composition and form a pressure-sensitive transfer layer on said metal-coated foundation while the foundation is maintained grounded, thereby avoiding the possibility of static accumulation which attracts deleterious dust into the transfer composition and avoiding the possibility of static discharge which could cause combustion of the organic solvent particularly during the evaporation thereof.

7. The process of avoiding the hazards of static electricity while coating a continuous flexible plastic film foundation having a tendency to accumulate static electricity with an organic solvent-applied transfer composition, which comprises vacuum coating said foundation with a thin flexible conductive metal layer comprising silver, grounding said metal-coated foundation to allow the static electricity to be conducted therefrom and coating said grounded metal-coated foundation with a layer of transfer composition comprising resinous binder material, imaging pigment and a volatile organic solvent, and evaporating said solvent to solidify said transfer composition and form a pressure-sensitive transfer layer on said metal-coated foundation while the foundation is maintained grounded, thereby avoiding the possibility of static accumulation which attracts deleterious dust into the transfer composition and avoiding the possibility of static discharge which could cause combustion of the organic solvent particularly during the evaporation thereof.

(References on following page) 5 6 References Cited by the Examiner 3,036,549 5/ 1962 Iwata et a1 117-107.1

Newman et al. 2/ 1952 Famulener et a1. FOREIGN PATENTS 2/ 1956 Toulmin 117107.2 5 485,250 10/ 1929 Germany, 3%; fiz f f WILLIAM D. MARTIN, Primary Examiner. 4/1958 Clancy et a1 117-363 MURRAY KATZ, Examiner- 

1. THE PROCESS OF AVOIDING THE HAZARDS OF STATIC ELECTRICITY WHILE COATING A CONTINUOUS FLEXIBLE FOUNDATION HAVING A TENDENCY TO ACCUMULATE STATIC ELECTRICITY WITH AN ORGANIC SOLVENT-APPLIED TRANSFER COMPOSITION, WHICH COMPRISES COATING SAID FOUNDATION WITH A THIN FLEXIBEL CONDUCTIVE METAL LAYER, GROUNDING SAID METAL-COATED FOUNDATION TO ALLOW THE STATIC ELECTRICITY TO BE CONDUCTED THERFROM AND COATING SAID GROUNDED METAL-COATED FOUNDATION WITH A LAYER OF TRANSFER COMPOSITION COMPRISING BINDER MATERIAL, IMAGING MATERIAL AND A VOLATILE ORGANIC SOLVENT, AND EVAPORATING SAID SOLVENT TO SOLIDIFY SAID TRANSFER COMPOSITION AND FORM A PRESSURE-SENSITIVE TRANSFER LAYER ON SAID METAL-COATED FOUNDATION WHILE THE FOUNDATION IS MAINTAINED GROUNDED, THEREBY AVOIDING THE POSSIBILITY OF STATIC DISCHARGE WHICH COULD CAUSE COMBUSTION OF THE ORGANIC SOLVENT PARTICULARYLY DURING THE EVAPORATION THEREOF. 